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Banana slug is a common name for three species of air-breathing land slug in the genus Ariolimax. These slugs are often yellow in color and are sometimes spotted with brown like a ripe (or overripe) banana.

Ariolimax is a genus of terrestrial pulmonate gastropod molluscs in the family Ariolimacidae.

Ariolimax is the type genus of the family Ariolimacidae. It was previously placed in the family Arionidae.

Species

Species within the genus Ariolimax include:

• Ariolimax californicus J. G. Cooper, 1872 — California banana slug^[1]
• Ariolimax columbianus Gould, 1851 — Pacific banana slug^[1]
• Ariolimax dolichophallus Mead, 1943 — Slender banana slug^[1][2][3]

Description

Banana slugs are often bright yellow (giving rise to the banana sobriquet) although they may also be green, brown, or white. Some slugs have black spots (Ariolimax columbianus) which may be so extensive as to make the animal look almost solid black.

The Pacific banana slug is the second-largest species of terrestrial slug in the world, growing up to 25 centimetres (9.8 in) long,^[4] and weights of 115 gram (4 oz).^[5] (The largest slug species is Limax cinereoniger of Europe, which can reach 30 centimetres (12 in) in length.)

Banana slugs can move at 6 ½ inches (16.5 cm) per minute.^[6]

Head and tentacles of a banana slug

Slugs use two pairs of tentacles to sense their environment. The larger, upper pair, termed "eyestalks," are used to detect light or movement. The second, lower pair are used to detect chemicals. The tentacles can retract and extend themselves to avoid damage.

Banana slugs have a single lung which opens externally via pneumostome. The pneumostome lung cavity is heavily vascularized to allow gas exchange. Dehydration is a major problem for the mollusk. Banana slugs excrete a thick coating of mucus around their bodies and can also estivate. They secrete a protective layer of mucus, and insulate themselves with a layer of soil and leaves. They remain inactive in this state until the environment is moist again.

Courtship

The slime also contains pheromones to attract other slugs for mating. Slugs are hermaphrodites, and reproduce by exchanging sperm with their mate. They produce up to 75 translucent eggs, which are laid in a log or on leaves. Slugs mate and lay eggs throughout the year. The adults provide no further care for their eggs beyond finding a suitable hiding spot, and the eggs are abandoned as soon as the clutch is laid.^[7]

Distribution

Ariolimax columbianus is native to the forest floors along North America's Pacific coastal coniferous rainforest belt (including redwood forests) which stretches from Southeastern Alaska to Santa Cruz, California.

Several discontinuous populations do also occur in forested slopes of the coastal and traverse mountain ranges south of Santa Cruz as far south as Ventura County, with a tiny, isolated population located in Palomar Mountain State Park within the Palomar Mountain Range in San Diego County, California. The Palomar Mountains have lush Sierra Nevada-like coniferous forests and black oak woodlands unlike the surrounding semiarid lands of inland San Diego County and mark the southernmost population of banana slugs. The slugs were rediscovered several years ago along Doane Creek, part of the Lower Doane Valley/Lower French Trail. This population is believed to be a relict from the Pleistocene epoch when the climate was cooler and wetter.

Small, isolated populations also occur east of the Pacific Coast such as in the inland coniferous rainforests of British Columbia's Columbia Mountains (interior wet-belt), just west of the Canadian Rockies, and have been seen at lower elevations near creeks and damp areas of Mount Revelstoke National Park. Small populations of banana slugs have also been seen along creek and damp areas of the western slopes of the Sierra Nevada mountains to the north of Yosemite National Park in California. Slug densities in these outlying areas in the Columbia Mountains, Sierra Nevada Mountains, and areas south of Santa Cruz are low compared to densities in the coastal coniferous rainforest belt and are rather restricted to damp areas near creeks, ravines, and gullies.^[7] This population is probably also a relict from the Pleistocene epoch.

Ecology

Banana slugs are detritivores, or decomposers. They process leaves, animal droppings, and dead plant material, and then recycle them into soil humus[1]. They seem to have a fondness for mushrooms, and they spread seeds and spores when they eat, and excrete a nitrogen rich fertilizer.^[7][8] By consuming detritus (dead organic matter) slugs contribute to decomposition and the nutrient cycles^[9] and are an important aspect of the ecosystem.

Raccoons, garter snakes, ducks, geese and salamanders sometimes eat banana slugs; they roll the slugs in soil to bind the slime. Juvenile banana slugs are sometimes eaten by shrews or moles.

In culture

Banana slugs have been used as food by Yurok Indians of the North Coast and by German immigrants in the 19th and early 20th centuries. A yearly festival and contest is held at Russian River (California) including slug races and a contest for recipes - though, even when fed corn meal to purge them or soaked in vinegar to remove slime, the slugs' flavor is not always well regarded, and the most successful entries are often those in which the flavor is unnoticeable.^[10][11]

The banana slug is the mascot of the University of California, Santa Cruz.^[12]

The album artwork for Thirteenth Step by A Perfect Circle features a banana slug crawling across a woman's face.

In one of the scenes in the film Coraline (film), Wyborne "Wybie" is seen hunting banana slugs along with his cat in the mist.

References

Wikispecies has information related to: Ariolimax

Wikimedia Commons has media related to: Ariolimax

• Schad, Jerry, "Afoot & Afield in San Diego County", Wilderness Press, 1998.